The present invention relates to filter units for use with septic systems and more particularly to a filter unit disposed within a septic tank having a controlled outlet flow rate.
There are a number of filtration systems known in the prior art for use in a septic tank to remove the solid materials from the waste water prior to the waste water being discharged from the septic tank. One of the earlier references of which I am familiar is U.S. Pat. No. 2,900,084 which issued to Zabel. U.S. Pat. No. 2,900,084 teaches a septic tank having its interior arranged to provide a U-shaped path of flow wherein one leg of the U constitutes an upstream chamber which receives incoming sewage through a tank inlet at a high inlet level and is normally filled therewith up to an intermediate stagnant level spaced substantially below the high inlet level and the other leg of the U constitutes a downstream chamber which receives partially or completely digested sewage from the upstream chamber through the bight of the U and is normally filled therewith up to the intermediate stagnant level and which discharges a clarified effulent through a tank outlet when additional sewage pours into the upstream chamber and thus causes the downstream chamber to overflow at a stagnant level. Particularly, this reference teaches a cylindrical casing vertically arranged with the outlet end portion of the tank forming the downstream chamber with an inlet opening at its bottom and a sidewall outlet at the top side of the stagnant level. An outlet trap arranged within the casing to separate solids from the fluid material overflowing the downstream chamber and to provide an outlet passageway directing that overflow into a tank outlet is also provided.
More recently, U.S. Pat. No. 4,710,295, which also issued to Zabel, teaches a filter unit for use in a casing disposed in a septic tank which includes a plurality of vertically stacked disc-dam units forming a cartridge having a longitudinal axis on each disc-dam unit with a generally circular planar base and a chord edge. The chord edge of each disc-dam unit is in mutual alignment so that first and second sealing edges are formed through perspective ends of the chord edge with the first and second sealing edges being parallel to the longitudinal axis. Each disc-dam unit or base includes a continuous elongate dam located on one side of the base and extends outwardly therefrom to terminate at a dam top where the elongate dam has a dam first end adjacent to the first sealing edge and extends continuously to a dam second end at the second sealing edge to divide the base into an upstream and downstream side with a retaining device to hold the disc-dam units in stacked relation with selected spacing between the dam top of one disc-dam unit and the bottom surface of the next vertical-above unit.